algae

Turns out life in the gutter is not all bad. Scientists have just discovered that gutters lining the streets of Paris are teeming with microscopic life that may help improve water quality of urban storm water runoff.

The research team, comprised of biologists from the BOREA Biology of Aquatic Organisms and Ecosystems research unit in France and a fellow scientist from the Max Planck Institute for Terrestrial Microbiology in Germany, have found that gutters running alongside Parisian streets provide an oasis for a myriad of microscopic organisms, including fungi, microalgae and sponges, as well as mollusks. These urban aquatic communities may provide beneficial ecological services, for example helping to clean storm water and reducing urban waste by breaking down solid organic matter as well as urban contaminants such as engine oil and vehicle exhaust fumes that could otherwise degrade water quality. Gaining a clearer understanding of what organisms make up these communities, and the ecological niche they fill, can help us better understand the ecological services that gutter ecosystems render.

A storm water drain in Paris

The results of the study, which is the first to shed light on the complex biodiversity of microorganisms living on the streets of Paris, appeared in the October 2017 edition of the ISME Journal.

After noticing the characteristic brown and green tinge of the water flowing in Paris city gutters, as well as bubbles — which are a tell-tale sign of photosynthesis taking place, BOREA researchers suspected that there may be microalgae present in the water. So they set about analyzing non-potable water samples they collected from various locations to identify what microorganisms were present. Sample sites included street gutters, water outlets located on street curbs that pump water from either the Seine or the Canal de l'Ourcq which is used for street cleaning, as well as water collected directly from the Canal de l'Ourcq and the Seine.

They identified a remarkable 6,900 possible species of eukaryote microorganisms in the roughly one hundred water and biofilm samples they collected off the streets of Paris. Unicellular diatoms were the most abundant, but other unicellular eukaryotes (organisms with a nucleus and organelles) such as amoebas, Rhizaria and alveolates; fungi (including species that are recognized as decomposers); sponges; and even mollusk species were observed. More surprising, the researchers around 70% of the species detected in gutter water were not present in the non-potable source water. The composition of the microorganism communities varied greatly between the sites sampled, which according to the researchers, suggests they may originate as a result of human activity or that they have adapted to thrive in the specific urban location where they are found.

The researchers conclude that gutters on city streets and the microorganisms they support seem to represent a unique ecosystem that may have a specific, but as yet undiscovered, ecological role to fulfill. Clearly intrigued, the scientists stress that we need to know more about these microorganisms: What exactly are they? What function do they serve? Do they play a key role as minute curbside treatment plants, helping to clean wastewater? How have they adapted to life on the city streets? Should we be monitoring them more closely? To answer these questions, the researchers hope to expand this study by looking at other forms of life, such as bacteria, over a longer timeframe, and assessing microscopic life in gutter water of other cities too.

Nitrate-rich agricultural runoff is considered one of the key factors contributing to harmful algal blooms in coastal zones. The Gulf of Mexico is particularly vulnerable to harmful algal blooms for two reasons:

1) It is a large bay with slow water turnover rates, exacerbated by strong onshore winds; and

2) Many of the watersheds feeding into it flow through agricultural lands.

Now a new study, which was recently published in the scientific journal Ecology Letters, examines the link between agricultural runoff and harmful algal blooms in the Gulf of Mexico, The study looks at how the silica:inorganic-nitrogen ratio in the water of 130 lakes that feed into the Gulf of Mexico influence nutrient levels in these coastal waters.

Satellite Image of Gulf of Mexico Algae Blooms

The study is important, especially considering that during 2016 the Gulf experienced an above average sized dead zone as a result of a combination of agriculture, algae and weather patterns. Long-term records of water chemistry in the Gulf of Mexico show that the silica:inorganic-nitrogen ratio has changed dramatically over the last century, shifting more towards nitrogen. There are two potential explanations for this shift: 1) silica may be removed by reservoirs and dams dotted along the watershed; and 2) the input of nitrogen (from nitrate-rich fertilizers) from agricultural runoff is so high that it forces the ratio of silica:nitrogen downward. This new study shows that silica is not removed by dams and reservoirs, and that nitrogen levels increase dramatically when agriculture makes up more than 60% of the landscapes feeding into the system.

In coastal zones, such as the Lake Erie and the Gulf of Mexico, high concentrations of dissolved nitrogen fuel algal growth, which leads to oxygen depletion, or coastal dead zones. In normal conditions, where the ratio of silica:nitrogen is in balance, diatoms — which are effectively the lungs of the planet — are able to survive. Yet, when the chemical balance is tipped towards nitrogen, the phytoplankton community is altered. Diatoms — beneficial algae that we want to see in the Gulf of Mexico — thrive when the levels of silica and nitrogen are in balance. When conditions tend to be more nitrate-rich, other more harmful species of phytoplankton thrive.

The research team found that an increase in nitrogen runoff from agricultural fields explains why the Gulf of Mexico is continually plagued by harmful algal blooms. The scientists also identified ways in which landscapes could be better managed to improve water quality in the watersheds and coastal zones they feed into. They recommend that landscapes be managed at watershed level to significantly enhance water quality, particularly during wet years. They also suggest that reservoirs and dams could be key areas to target to diminish nutrient loads without impacting silica concentrations of water flowing into the Gulf of Mexico.

"We need to be vigilant about our land use and water quality," said co-author John Downing, director of the University of Minnesota Sea Grant College Program and the study's principal investigator. "Climate change and increased storminess will likely exacerbate the skewed ratios we found and the extent of harmful blooms in coastal areas if we don't manage agricultural runoff more effectively. Harmful algae blooms cost the U.S. seafood, tourism and health industries over $80 million a year according the National Oceanic and Atmospheric Administration, and we know we can do better."

Microalgae are tiny single-celled plants known phytoplankton that can be both a boon and a bane. They form the base of marine and freshwater food chains, providing an essential food source for fish and other freshwater and marine species. Additionally, they absorb roughly half of all carbon dioxide released on Earth through the process of photosynthesis. However, some species (e.g. cyanobacteria) produce phyto-toxins that can be harmful to fish and wildlife, as well as humans and domestic animals. When conditions are right, phytoplankton can flourish, resulting in a population explosion -- or algal bloom -- which can extend over vast areas, as is common in Lake Erie, where a 2014 outbreak resulted in a drinking water ban in Toledo, Ohio, which affected close to half a million residents.

Now, the US Environmental Protection Agency (EPA) with financial assistance from NASA are developing a cellphone app that will allow them to track harmful algae species that pose a threat to the nation's drinking water supplies. This will not only have health benefits, but economic benefits too. Freshwater contamination by harmful algae results in an economic cost/loss of around 64 million US dollars annually.

The EPA, NASA, National Oceanic and Atmospheric Administration (NOAA) and the US Geological Survey (USGS) have put their heads together to come up with a solution. NASA has been using Earth observing satellites to detect and monitor algal blooms in coastal zones for some time now, but have now adapted this to enable them to monitor water quality of freshwater systems too. Soon water quality managers will be able to determine the quality of the water simply by looking at their cellphones.

The research team, comprised of scientists from all four agencies, are currently collaborating on a joint project that will enable them to transform satellite data into an indicator that can be used to detect cyanobacteria blooms in freshwater systems that supply us with water. The EPA plan to integrate this data into an Android smart phone app that will allow water managers and environmental officers to determine the water quality of a specific waterbody at a glance.

"With our app, you can view water quality on the scale of the US, and zoom in to get near-real-time data for a local lake," explains the EPA's Blake Schaeffer, Principal Investigator for the project. "When we start pushing this data to smartphone apps, we will have achieved something that's never been done – provide water quality satellite data like weather data. People will be able to check the amount of 'algae bloom' like they would check the temperature."

How Does the App Work?

Harmful cyanobacteria species emit chlorophyll and fluorescent light during their life cycle. These 'ocean color' signals can be detected by satellite systems, such as NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat, and the European Space Agency's Sentinel-2 and Sentinel-3, revealing both the location of the cyanobacteria and their abundance. The researchers will gather this data for freshwater systems and convert it into a format that is readily accessible via the cellphone app or web portals.

By enabling water managers at treatment facilities to have an early warning system alerting them to developing harmful blooms that threaten water quality, they will be in a better position to take the necessary steps to prevent contamination by upping water treatment dosages where necessary to keep residents safe, while at the same time avoiding unnecessary over treatment, that can be costly. This information will give park managers early warning to potential health risks, and assist them to take action to keep recreational users of water bodies, such as swimmers and kyakers, safe.

NASA's Administrator Charles Bolden says: “We’re excited to be putting NASA’s expertise in space and scientific exploration to work protecting public health and safety."

It is anticipated that this project will also help scientists to gain a better understanding of why harmful algal blooms occur -- what are the environmental triggers that fuel their growth. By comparing algal outbreak color data with data on land cover change, they hope to get a clearer picture of what environmental factors spur these blooms. The end result will be: improved forecasts of algal bloom events, together with a clearer understanding of when an algal bloom is likely to be harmful or harmless.

Over the last few decades there has been an increase in toxic algal blooms in aquatic systems around the world primarily as a result of climate change and nutrient enrichment, which results in an abundance of toxic cyanobacteria, such as microcystin – a prolific cyanotoxin found worldwide that poses a serious threat to wildlife, natural ecosystems and human health. Microcystin is a potent liver toxin that is also potentially carcinogenic; consequently, it poses a serious health risk as a drinking water contaminant.

According to a study conducted by a team of scientists from Oregon State University and the University of North Carolina at Chapel Hill, which was recently published in Science, the proliferation of toxic strains of cyanobacteria will increase proportionately as nutrient enrichment increases in freshwater systems.

Toxic microcystin bacteria float, along with a dead fish, on the surface of this lake.

Cyanobacteria

Cyanobacteria are one of the oldest living organisms on our planet. They evolved around three-and-a-half billion years ago in an oxygen-free, barren world devoid of most life-forms, and by producing oxygen, played a fundamental role in transforming this lifeless world into what it is today and allowing higher life-forms to evolve. According to the scientists, these early pioneers readily adapt and persist in the environment and as our world changes they are once again adapting to changing environmental conditions, and to an extent threatening some of the life they originally allowed to develop.

Microcystis

Microcystis, a species of microcystin-producing cyanobacteria that flourishes in warm, slow flowing, nutrient-rich waters all over the world – is a strain that is particularly worrisome. It is able to migrate vertically within the water column, typically forming thick green algal mats on the water's surface. When conditions are optimal these toxin-producing cyanobacteria flourish and quickly out-compete and displace non-toxic cyanobacteria, resulting in algal blooms that are becoming more and more harmful.

“Cyanobacteria are basically the cockroaches of the aquatic world, they're the uninvited guest that just won't leave,” said Timothy Otten, a postdoctoral scholar in the OSU College of Science and College of Agricultural Sciences, and co-author of the study. “When one considers their evolutionary history and the fact that they've persisted even through ice ages and asteroid strikes, it's not surprising they're extremely difficult to remove once they've taken hold in a lake. For the most part, the best we can do is to try to minimize the conditions that favor their proliferation.”

There are over 123,000 large lakes (> 10 acres) spread throughout the US, and according to the latest EPA assessment a third or more contain toxic cyanobacteria. In some cases, such as Lake Erie, the area covered by algal blooms can be so vast that it is visible from space. Increasing temperatures and CO2 concentrations; dams; droughts; as well as nutrient runoff from agriculture, recreational and private land all exacerbate the situation.

Toxicity of Cyanobacteria and Microcystin

Scientists studying cyano-toxins believe that since cyanobacteria evolved before predators, it is unlikely that their original function was to be toxic. Recent studies suggest that microcystin – a potent liver toxin and potential carcinogen – has a protective function in cyanobacteria, helping them cope with oxidative stress, which may explain why the genes responsible for synthesizing the toxins are so ubiquitous across cyanobacteria species and why they still persist millions of years after they evolved.

Because cyanobacteria need light to proliferate and the toxins are retained primarily within the microorganism, the risk of exposure is greatest on or near the surface of the water, which poses a danger to bathers, kayakers and other recreational users.

“Also, since cyanobacteria blooms become entrenched and usually occur every summer in impacted systems, chronic exposure to drinking water containing these compounds is an important concern that needs more attention,” Otten said.

“Water quality managers have a toolbox of options to mitigate cyanobacteria toxicity issues, assuming they are aware of the problem and compelled to act,” Otten said. “But there are no formal regulations in place on how to respond to bloom events. We need to increase public awareness of these issues,” he stresses. “With a warming climate, rising carbon dioxide levels, dams on more rivers than not, and overloading of nutrients into our waterways, the magnitude and duration of toxic cyanobacterial blooms is only going to get worse.”